photosphere

The structure of the Sun. Nuclear reactions at the core release vast amounts of energy in the form of light and heat that radiate out to the photosphere and corona. Surges of glowing gas rise as prominences from the surface of the Sun and cooler areas, known as sunspots, appear as dark patches on the star's surface.

Visible surface of the Sun, which emits light and heat. About 300 km/200 mi deep, it consists of incandescent gas at a temperature of 5,800 K (5,530°C/9,980°F).

Rising cells of hot gas produce a mottling of the photosphere known as granulation, each granule being about 1,000 km/620 mi in diameter. The photosphere is often marked by large, dark patches called sunspots.